1. Field of the Invention
The invention relates to signal receiving technology in a wireless communication system, and more particularly to a channel estimation method and device in an orthogonal frequency division multiplexing (OFDM) system.
2. Description of the Related Art
In the recent years, orthogonal frequency division multiplexing (OFDM) has been widely used due to its capability of reducing multi-path interference and high spectrum efficiency. The OFDM is capable of supporting multiple accesses for multiple users. In particular, the orthogonal frequency division multiple access (OFDMA) technique in combination with the frequency division multiple access (FDMA) technique efficiently controls the data rate of each user. Thus, channel utilization is improved. For example, in the system complying with the 802.16e standard, also known as a Worldwide Interoperability for Microwave Access (Wimax) system, the combination of OFDM and multiple in multiple out (MIMO) antenna technologies is introduced in the physical layer of the transmission protocol so as to double the transmission rate and support sufficient mobility. Such kind of system is able to provide non light of sight data transmission in the 2 GHz˜11 GHz band with 20 MHz bandwidth. The data transmission rate achieves 75 Mbps with a 10 km radius coverage and mobility achieves 120 km/h.
However, in the wireless communication system, the data transmission is often affected by frequency selective fading and time variance of the channel. In a wireless terminal, channel estimation of the possible effects as described above during the data transmission is required. Specifically, at a signal receiving terminal, the channel information is required for quantization and decoding. Thus, channel estimation is a key technology for wireless data reception and process.
The Wiener filter is widely used in the current channel estimation methods to obtain channel information and filter with finite impulse response based on the tap coefficient determined by channel characteristics. Such kind of method reveals both the time variant and frequency selective fading characteristics of the channels.
However, large amount of multiplications are required when obtaining the filter coefficients of the Wiener filter. Although the complexity of an order 2 Wiener filter may be reduced, it still requires large amount of operations due to the large number of pilot sub-carriers in the frequency domain. Thus, efficiently and easily obtaining information about the Wiener filter coefficients is a key issue.